1.25x^2-3.75x-5=0

Solution for 1.25x^2-3.75x-5=0 equation:

1.25x^2-3.75x-5=0

a = 1.25; b = -3.75; c = -5;
Δ = b2-4ac
Δ = -3.752-4·1.25·(-5)
Δ = 39.0625
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-3.75)-\sqrt{39.0625}}{2*1.25}=\frac{3.75-\sqrt{39.0625}}{2.5}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-3.75)+\sqrt{39.0625}}{2*1.25}=\frac{3.75+\sqrt{39.0625}}{2.5}
$